just so you know, IE6 does not time gifs properly. newest versions of FF and Opera do, however. I can't vouch for IE7 or 8, Safari, Chrome etc.
I like the style, but there are a few thinss that could be improved here.
I'm pretty bad about explaining these things verbally, i'll have an edit up here in just a bit.
Edit up.
It's like 4:30 in the morn here so i apologize if none of this makes any sense.
Frame 4 - trimmed down the 'blur' from the swing a bitit looks a little more sharp. sharper = more ouch factor.
Frame 5 - cut out some of the bottom end of the swing blur. Because frame 6's blur previously occupied the same space, I thought it would look a little smoother if i did what i did. (frame 5's blur and frame 6's blur overlapped quite a bit and made much of frame 6 redundant. ) als moved a fair bit of his head and torso down and to the right, to make it look like he's putting more of his body into the swing. Swinging a swordrbaseball bat/giant frozen fish requires you entire body to move in tandem. it's hnot perfect but i think it gets the message across a bit better.
Frame 6 - Extended the blur a tad, gives that frame more visual priority. moved the head southeast again.
frame 7 - this is the one i added in. It's not particularly important, but moved the sword to the right and angled it up a bit, also moved the shield up 1 pixel to make it seem like there's a wee bit of heft to his gear.
frame 8 - added this one in. it's the exactly the same as frame 6 from your version cept i took out the blur entirely, and i moved the shield down 1 pixel.
frame 9 - didn't touch it.
I also messed with the timing all over the place, can't remember where now
Removing frame 8 would just about preserve the "quickness" of your original. Personal drawback. I tend to focus on fluidity too much and it ends up sucking all the force out.